1. Field of the Invention
The present invention relates to an ophthalmological instrument such as a retinal camera. More particularly, the present invention relates to such ophthalmological instrument which is able to continuously change the magnification for observation or for picture taking.
2. Description of the Prior Art
In ophthalmological instruments such as retinal cameras there is used such optical system which produces no vignetting effect with respect to a diaphragm disposed conjugate with the cornea of an eye being examined. In such an optical system, the diaphragm conjugated with the cornea functions as a diaphragm for the whole optical system and also it determines the position of an eye point for observation. Ophthalmological instruments comprising such optical system have a disadvantage. As is known to those skilled in the art, the disadvantage is found in the fact that when the magnification for observation is continuously changed, the position of the eye point is also subjected to change which makes it difficult to obtain good observation.